The present invention relates to methods for preparing nonaqueous, microparticle dispersions.
There have been numerous and varied approaches to the preparation of microparticle dispersions in nonaqueous media. Each approach has possessed its own inherent disadvantages, largely stemming from the mode of preparation. For example, difficulties which have been prevalent in prior art modes of preparation are the inability to achieve a dispersion which is uniformly of a small particle size, on the order of less than five microns, preferably less than one micron. In addition, generally because of the large particle size, nonaqueous microparticle dispersions have suffered from the lack of stability especially when the continuous phase is of low viscosity. This typically means that the dispersion either settles upon standing or coagulates and forms large clumps.
There is a need, therefore, for a simple, efficient, economical way to prepare stable nonaqueous microparticle dispersions having a uniformly small particle size.